Epoxy grout is the best grout you can have in a bathroom: easy to clean, flexible, not absorbent, and waterproof.
In certain situations, we would only use epoxy grout: when using underfloor heating. Both of these options benefit the most from the epoxy grout properties.
Unless your quote mentions epoxy grout, there will be an extra charge if you prefer epoxy grout instead of cement-based grout